Plasma processing systems are used in the manufacture and processing of semiconductors, integrated circuits, displays, and other devices to both remove and deposit materials on a substrate such as a semiconductor wafer. Plasma processing of semiconductor substrates to transfer a pattern of an integrated circuit from the photolithographic mask to the substrate, or to deposit dielectric or conductive films on the substrate, have become standard methods in the industry.
Halogen-containing and carbon-containing gases are commonly used to etch dielectric layers such as oxides and newer low-dielectric constant (k) materials. These gases are known to generate fluorocarbon polymer reaction products, that can deposit on internal surfaces of a process chamber including chamber components and chamber walls. Over time, these residues can accumulate in the process chamber and may eventually flake off, thereby generating particle contamination in the process chamber and on processed substrates. Furthermore, these residues and fluorine radicals in the process environment begin to participate in the etch process in ways that can affect the etch rate, etch profile, critical-dimension control, wafer uniformity and selectivity. This is commonly referred to as the fluorine/polymer memory effect.
To control the amount of chamber residues, plasma processing systems must be periodically shut down for scheduled, and sometimes unscheduled, wet chamber cleans. Wet cleans reduce system availability, lower productivity, and add the cost of non-production (dummy) wafers for chamber conditioning to production expenses, all of which increase the system cost of ownership. The mean time between wet cleans (MTBWC), measured either by the number of wafers processed or as cumulative etch time, can be extended if the process chamber can be dry cleaned by an in-situ plasma cleaning process. However, conventional dry cleaning processes may not be effective in removing residue from the chamber interior. Moreover, conventional dry cleaning processes involve an aggressive chemical reaction that requires a wafer present on a substrate holder of the chamber in order to “shield” the sensitive materials of the substrate holder from being damaged by the dry cleaning process. This use of a substrate during dry cleaning decreases throughput of the chamber because shield substrates must be loaded into and removed from the chamber in order to perform the dry cleaning. The shield substrate also prevents the dry cleaning process from effectively cleaning residue from the substrate holder. The present inventors have recognized that this failure to remove residue from the substrate holder not only contributes to particle contamination as noted above, but also can cause arcing in electrostatic chucks, and otherwise prevent proper operation of this type of substrate holder.